Which stone for exterior wall

Hello,

You only achieve an order of magnitude of 0.035 W/m²K or even less with insulating materials made of mineral wool, EPS, etc.

Nope ...

Ahem, there I even see "only" a smallest value of 0.07. However, regarding the U-value, I hope you agree with me that 0.22 (just picked at random) W/m²K is greater than 0.035, right? If 0.35 (that is, one order of magnitude greater) was meant here, I doubt that a building method compliant with the energy saving ordinance is even possible with that. However, I admit that I was somewhat careless in not consistently distinguishing between W/mK (specific thermal conductivity, lambda) and W/m²K (U-value).

In any case, it remains that the construction specification was probably made more to confuse interested parties with important-looking values than to provide reliable information for the layperson.

Regards

K1300S

Hello K1300S and construction expert,

thank you for your feedback. Of course, the overall concept is important, that makes sense. However, as the client, I have to question individual parts of the concept and, as far as possible for a layman, get an idea.

Basically, I am doing nothing more than spot checks with the goal of questioning and gaining more certainty.

I have now asked our architect/engineer again precisely. The stone referred to in the construction specification "delivery and installation of a 42cm thick aerated concrete masonry PP2 WLG 0.35" is the following stone:

H+H efficiency stone, U-value=0.18, lambda=0.08, and would be roughly comparable to an efficiency house 55. What do you think? Sounds good, right?

I also asked him again whether it would not be better to use a Poroton T9. He said that this is of course feasible and would be roughly the same price material-wise. But: various tradesmen (electricians, plumbers, etc.) would not like to work with Poroton because it often breaks when cutting/slitting. Independent of the fact that heat bridges would more easily form at the fracture points (which would be closed with insulating mortar or similar), the tradesmen would also quickly charge more for their services in the tenders than with the much simpler aerated concrete stone (e.g., H+H). That sounds plausible at first, I have no idea if this is actually the case. But I trust him (he is not a developer). Furthermore, Poroton would be more common in central and southern Germany. In northern Germany, many tradesmen would be very reluctant to install it and would not actively offer it.

H+H efficiency stone is one of the best aerated concrete stones.

There is no such thing as the "best" stone anyway. As linked in Epi's post, Ytong even offers 0.07 – and in Denmark even 0.06. They insulate even better. But the overall concept is what's important. What is supposed to be achieved? KfW55?

I still don't understand what the WLG 0.35 is supposed to mean (it just doesn't fit), but whatever.

The regionally different construction methods are true, although I assume that both (aerated concrete and hollow brick) can deliver similar results. I don't know if an electrician asks about the masonry in advance. With the right tools, neither is a problem. Also, no thermal bridges certainly occur at the break points, because the insulation stays in place. Clay hardly insulates at all, after all.

However, you should consider that, for example, not every dowel holds in aerated concrete. For that reason, I decided on Poroton back then and have not regretted it so far.

Thank you, K1300S. That was not meant that way either. He said "under the aerated concrete blocks, the H+H efficiency block would be the best." Are there differences between Ytong, Hebel, H+H, etc.?

We do not plan any additional insulation. Only interior and exterior plaster (over reinforcement mesh... or similar).

Counter-question: Are there differences between Audi, BMW, and Mercedes? (Answer: The differences here are probably very small and are presumably primarily related to the price or delivery costs due to the distance from the factory.) As mentioned, if H+H is currently at 0.08 W/mK "at the limit," then this is "the best insulating aerated concrete block from H+H" – but Ytong can top that with 0.07 W/mK. At least according to the measured values. Whether that is seriously relevant in practice is another matter.

Still, the question again: Do you want/need to achieve a certain efficiency standard or should it simply be "just" sensible? We decided back then on the T7 because there was virtually no difference to the T8. But that does not always have to be the case.

Best regards

K1300S